| How to clean the pressed snow on speedway, highway and urban street during the winter has always been an important subject which attracted much attention around the world. Snow cleaning has important social, economic, traffic and environmental impact on the inhabitants of large northern cities. With the development of society and mechanical technology, people more and more require an efficient and roboticized machine with which to clean snow and ice-snow. In order to improve the automatization level and efficiency of snow-clean vehicles, we try to develop and research a kind of highly roboticized,intelligent and technological machine that can detect the thick of snow layer and clean snow according to the surface of road in this thesis. So we require a more efficient hydraulic control system. At present, there are electro-hydraulic on-off control, electro-hydraulic proportional control and electro-hydraulic servo control three kinds of hydraulic control system in real application. And different system chooses different components as it's core. Proportional valve is a kind of hydraulic component between on-off valve and servo valve. It's cheaper and more anti-polluting than servo valve. And its performances are as good as servo valve's except precision and response speed. Its static and dynamic characteristic can meet the needs of most of industrial control system. Compared with classic on-off valve, though proportional valve is more expensive, its good control performance made some compensation. So we use proportional valve in those occasion where high control qualities are needed in stead of on-off valve. Besides, proportional valve has the function of hybrid control of flow, pressure and direction. All these factors make proportional valve control system has better control performance and more simple structure than classic on-off valve's. Considering the factors of synthesis performance requirement and cost, we choose the electro-hydraulic proportional valve system as the working device of multi-function snow-clean vehicles. The purpose of the study in this thesis is to find a suitable control strategy to improve the performance of the hydraulic position servo system. Firstly, the electro-hydraulic proportional position control system of multi-function snow-clean vehicle is analyzed systemically. The working principle and structure of hydraulic system and electrical control system of snow-clean vehicle's working device are introduced. Then we put forward the modularization design principle of software and hardware system. And make good prepare for the further study. Secondly, based on the analysis of the characteristics of system components, a mathematical model through reasonable simplification is built. We analyse the related parameters and system performances of the electro-hydraulic control system. At the research of control system, it is extraordinary important to build system mathematical model. It is a strong tool to design system, analyse system performance and improve system structure. Snow-clean vehicle control system structure is rather simple, so we choose transfer function as its mathematical model. By using the Simulink tool, the simulation of the open-loop system is done. The results of the experiments indicate that the presented model is exact. Finally, research on control strategy is a very important part in this thesis. In which feasibility is validated by simulation and experiments. In PID control, the phenomena of slowly oscillation around target value are analyzed, and some improved methods are put forward. A fuzzy controller is designed for the system and its robustness is proved. The problem of steady-state error in fuzzy control systems is analyzed through simulation and experiments. Based on conventional PID control and fuzzy control, fuzzy-intelligent PID hybrid control is adopted as the strategy to keep a good dynamic process and a better steady-state behavior. The experimental results prove that the presented method is reliable and effective. The expected control...
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